[Libav-user] Using av_dict_set to set options

Joel Ng blood_elves88 at yahoo.com.sg
Mon Nov 28 04:16:55 EET 2016


Hello, I have several questions about using av_dict_set(AVDictionary 
**pm, const char *key, const char *value, int flags) to set the options 
for input and output videos.

I am trying to translate several options from the FFmpeg binary usage to 
the libav-api, and I have trouble with some of them.

1. If I have multiple options to set (e.g. "-preset ultrafast", and 
"-tune zerolatency"), do I just use av_dict_set repeatedly, one after 
the other? Will they overwrite each other? I believe they do, since the 
documentation says "Set the given entry in *pm, overwriting an existing 
entry." How do I add more options then?

2. I used "-re" on FFmpeg. av_dict_set requires a key and value. How do 
I apply this option?

3. How would I translate this to an option:
"-x264opts 
crf=2:vbv-maxrate=4000:vbv-bufsize=160:intra-refresh=1:slice-max-size=2000:keyint=30:ref=1"
I have a feeling I have to set all these manually on my AVCodecContext 
object. True? Problem is, I can't find most of these options on the object.

Thank you.
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